My 5150 is dead :( TUBE AMP GURUS HELP!!!!

[Sloan]

Anytime something fries like that, I almost always suspect power tubes. Check the power tube sockets for arcing, it will leave black carbon like what's around that resistor. If you see evidence of arcing, clean the socket and reuse if you want, but often it will arc again - so it's best to just get a new socket (cheap).

Also, you might want to up the wattage rating for that resistor too - I generally try to upgrade stuff when I replace it and I like bigger resistors, had to even put some flameproof ones in a JCM2000 before.

By the looks of it, I wouldn't think the traces are going to be blown out, typically with a 1/4w resistor they just explode and don't really harm much else. If a larger wattage resistor, like a 5w gets really hot, they can burn pcb's or get hot enough to compromise the solder joint.


While the amp is open, you might as well use electronics cleaner in all your knobs and jacks to get rid of scratchy sounds, and check the condition of all their solder joints.

Enzo is just about the only one worth listening to on the Peavey forum.

Enzo knows what he's talking about, great guy.

 

[Jevil]

More people die hit by a lightning or eaten by shark than electrocuted by a Peavey amp.

 

[guitarguru777]

Ok so here we are nearly a year later with an update .....

Cleaned the board, traces were fine, put in a new resistor now the amp will power on but no standby light and no sound. Did some digging on the net and saw that the ceramic fuse being blown could be the culprit? I just want to be sure this is possible. Im going to replace it tomorrow but I want to be sure this could actually be the cause of the new problem.

 

[GuitarHack]

EDIT: I had a dud Poweramp tube and resistor (tube caused resistor to fail from memory, it was a few years ago). Replaced Resistor, Tube and Fuse..........................all OK a few years later.

EDIT+++: Looking at your pics now, I never had an obvious resistor fail like that. Mine was one of the big white ceramic Power resistors that LOOKED fine until I tested it with an Ohm meter.

Sorry. Didn't mean to lead you in the wrong direction.

 

[Sloan]

Ok so here we are nearly a year later with an update .....

Cleaned the board, traces were fine, put in a new resistor now the amp will power on but no standby light and no sound. Did some digging on the net and saw that the ceramic fuse being blown could be the culprit? I just want to be sure this is possible. Im going to replace it tomorrow but I want to be sure this could actually be the cause of the new problem.

Yes, you most definitely need to check all those internal fuses for continuity with a multimeter. Set it to diode test mode and make sure that there is continuity when you probe both ends of the fuses. Even if a fuse *looks* intact, it may be blown.

Also, do not just stick any fucking fuse you find in there, make sure it is the proper value specified either on the amp or schematic. Do not ever put in a fuse rated higher or anything else, only what it calls for.

It sounds like you had a typical power tube failure case here, and that almost always blows a fuse(s), that's why they are there, to keep from destroying other things.


Personally, my first steps would be

1. remove the blown resistor
2. clean the fuck out of the board with rubbing alcohol & toothbrush
3. test all immediate components connected to or around the failed resistor (fuses too!)
4. install new resistor and replace any parts that test bad
5. check amp without power tubes installed (with load/speaker connected) and see if anything goes wrong.

Also, check all power tube sockets for arcing. If you had a tube arc, it typically leaves carbon on the tube socket. If there is carbon, it creates a short since electricity will flow on it. Do not bother with cleaning carbon off of a tube socket, install a new socket.

This is also why it's important to clean as much carbon off as possible when a component catches fire/blows. If you are having problems with carbon shorting things, you have to find a way to bypass it, by maybe cutting it or jumping it with jumper wires etc...

 

[guitarguru777]

Thanks guys, yes everything else seems fine other then the fuses, board is clean although there is some residual burn on the board from the mini fire ...LOL

 

[53Crëw]

+1 to Sloan's comments. His steps should get you on the right track. Carbon traces can cause all kinds of problems, so make sure everything is cleaned well.

 

[53Crëw]

board is clean although there is some residual burn on the board from the mini fire ...LOL

Depending on how bad it is, you might want to clean that up as best as you can. Maybe use some light sandpaper to try and get rid of any black areas. You can then use a solder mask pen and cover over the affected area to make sure it's no longer conductive.

 

[Loren Littlejohn]

Man I'm pretty thankful that both voodoo and FJA are within an hours drive.